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| Listing 1 . A text version of Hello World. |
|---|
class TextHelloWorld{
public static void main(String[]args){
System.out.println("Text Hello World");}//end main
}//end class |
As mentioned above, this program does not require the use of Ericson's library. It can be compiled and executed using a batch file containing thecommands shown in Figure 5 . You should make certain that you can compile and execute this program before progressing to the graphicversion.
Note that this batch file must be placed in the same folder that contains the file named TextHelloWorld.java , and that folder must be your "current directory."
Also note that the term "-cp . " (note the space followed by a period) is probablysuperfluous on most computers. According to PATH and CLASSPATH , "The default value of the classpath is "." (note the period), meaning that ..."
Therefore, it should not be necessary to specify the classpath as "-cp . " to compile and execute the program on mostcomputers. However, on 09/10/14, I encountered a student's computer that did notcomply with the default described above and this prevented the student from being able to compile and execute the program. Including "-cp . " in the javac and java commands doesn't cause any harm. Therefore, I have updated the batch file commands shown in Figure 5 to include it. You can omit it if your computer doesn't need it.
| Figure 5 . Batch file for text version of Hello World. |
|---|
echo off
del *.classjavac -cp . TextHelloWorld.java
java -cp . TextHelloWorldpause |
Listing 2 contains the code for a graphic version of Hello World.
| Listing 2 . A graphic version of Hello World. |
|---|
import java.awt.Color;
class GraphicHelloWorld{public static void main(String[] args){Picture pix = new Picture(200,100);
pix.setAllPixelsToAColor(Color.RED);pix.addMessage("Graphic Hello World",15,50);
pix.show();}// end main
}//end class |
The program shown in Listing 2 causes the image shown in Figure 6 to be displayed when the program is compiled andexecuted.
Figure 6 - Hello World in graphics.
As mentioned above, this program does require the use of Ericson's library. It can be compiled and executed using a batch file containing thecommands shown in Figure 7 . You should make certain that you can compile and execute this program before progressing to morecomplex programs involving Ericson's library.
Note that this batch file must be placed in the same folder that contains the file named GraphicHelloWorld.java , and that folder must be your "current directory."
| Figure 7 . Batch file for graphic version of Hello World. . |
|---|
echo off
del *.classjavac -cp .;M:\bookClasses GraphicHelloWorld.java
java -cp .;M:\bookClasses GraphicHelloWorldpause |
Once again, the commands shown in Figure 7 assume that the bookClasses folder is in the root directory on the M-drive. The bookClasses folder will likely be in a different location on your computer.
This section contains a variety of miscellaneous information.
Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.
I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.
In the past, unknown individuals have misappropriated copies of my modules from cnx.org, converted them to Kindle books, andplaced them for sale on Amazon.com showing me as the author. I receive no compensation for those sales and don't know who doesreceive compensation. If you purchase such a book, please be aware that it is a bootleg copy of a module that is freelyavailable on cnx.org.
Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.
-end-
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